Switch apparatus



Oct. 2, 1962 E. H. KARLEEN 3,056,866

SWITCH APPARATUS Filed Nov. 16, 1959 INVENTOR. EDWARD H. KARLEEN ATTORNEY United States Patent Ofiice 3,056,866 Patented Oct. 2, 1962 3,056,866 SWITCH APPARATUS Edward H. Karleen, Freeport, Ill., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Filed Nov. 16, 1959, Ser. No. 853,286 5 Claims. (Cl. 200-67) The present invention is directed to an improved precision snap acting switch, of the general type disclosed in the P. K. McGaJl Patent 1,960,020, wherein the movement of the operating means of the switch which is required between the actuated and de-actuated condition of the switch is greatly reduced as compared to prior art precision snap acting switches of comparable basic construction.

In many condition control systems it is desired to maintain the condition being controlled at a particular datum with as little deviation therefrom as possible. In such systems where precision snap acting switches are utilized to control the condition maintaining means, the switch of course has a great deal to do with the manner in which the system operates inasmuch as it is the switch in conjunction with the condition sensing means which determines whether the condition maintaining means is operating or not. Therefore it follows that the differ ential movement of the switch has an important effect on the deviation from the datum encountered in the system remembering of course that other components in the system can also effect the magnitude of deviation from the desired datum.

The differential movement of a precision snap acting switch can be reduced by reducing the air gap between the normally open contact and the movable contact of the switch. However, in prior art snap acting switches of the type under consideration, the normal air gap between the movable contact when in engagement with the normally closed contact and the normally open contact is about 0.006" to 0.010 so that a reduction of the air gap can bring about a heel and toe condition during the actuation of the switch in that a portion of the movable contact can be engaging the normally closed contact while another portion of the movable contact can be engaging the normally open contact. This of course can not be tolerated.

With a switch incorporating the present invention, differential movement is reduced to a very great extent when compared to a similar switch without the invention. As described herein, differential is reduced by incorporating a portion effectively a spring leaf of two thickness in the snap acting system; or stated another way, by providing resilient means in association with a part of a resilient member of the snap acting system. As disclosed in the preferred embodiment herein, this takes the form of a spring leaf member disposed in overlying relationship with a spring leaf member of the snap acting system. The overlying spring leaf member is positioned between the support for the spring leaf member of the snap acting system it overlies and the actuating area of the snap acting system.

It is not known why the differential of a switch is reduced through the utilization of the present invention, but it does appear that to attempt to explain the phenomenon involves the use of mathematics of a very high order. In any event differential movement is dramatically decreased as will be brought out below without detrimental effects being realized either as to the mechanical or electrical characteristics of the switch. Thus, the reduced differential is not accompanied by the undesirable heel and toe condition which is encountered when differential is reduced by reduction of the air gap between the appropriate contacts. Further, dead break is not encountered in switches utilizing the invention as might be suspected would arise when an additional member is arranged to be associated with a portion of the switch in the actuating area thereof.

Therefore, it is an object of the present invention to provide a precision snap acting switch with greatly reduced differential as compared to a similar switch without the invention.

Another object of the present invention is to provide a precision snap acting switch with greatly reduced differential without encountering the heel and toe condition or a dead break condition. A further object of the present invention is to provide a precision snap acting switch with greatly reduced differential by utilization of resilient means in conjunction with a resilient member of the snap acting system.

Still another object of the present invention is to provide a precision snap acting switch with greatly reduced differential wherein a portion of the snap acting system is effectively a spring leaf of two thicknesses.

These and other objects will become more apparent from a reading of the following specification and appended claims in which:

FIGURE 1 is a cross sectional 'view of precision snap acting switch incorporating the invention; and

FIGURE 2 is an exploded view of the structure of FIGURE 1.

In FIGURES l and 2, a precision snap acting switch (of the proportions disclosed in the H. Millard Patent 2,600,564 and of the form disclosed in the H. Millard Patent 2,627,754) includes a housing 10 comprised of a molded plastic base 11 and a molded plastic cover 12 appropriately fastened together. A first terminal insert 15 -is molded in the base 11 and includes a contact supporting member 16 having a first fixed contact 17 supported therefrom. A second terminal insert 20 is also molded into the base 11 and includes a contact support member 21 having a second fixed contact 23 supported therefrom. A third terminal insert 25 is likewise molded into the base 11 and includes a support member 26 disposed on the upper extremity 25a thereof. Also disposed on the upper extremity 25a of the terminal insert 25 is a leaf spring 30 which includes a compression member 31 and a pair of tension members 32. The tension members 32 of the spring leaf 30 are supported in cantilever fashion from the upper extremity 25a of the terminal insert 25 and the compression member 31 of the spring leaf 30 is supported in cantilever fashion from the upstanding leg 26a of the support member 26 with the free and movable extremity 33 containing a contact 34 disposed between the fixed contacts 17 and 23 with the movable contact 34 in engagement with the fixed contact 17 so as to form a snap acting system. Overlying a portion of the spring leaf 30 is another spring leaf 40 which for convenience is disposed on the upper extremity 25a of the terminal insert 25 and which is approximately the same thickness as the spring leaf 30 and of the same general outline as the portion of the spring leaf 30 that it overlies. The upper extremity 25a of the terminal insert 25 is upset so as to maintain the support member 26, the spring leaf 30 and the spring leaf 40 in position.

A plunger 45 includes an upset metallic pin 46 which is disposed in an opening 47 of the cover 12. lviolded about the lower extremity of the pin 46 is a plastic shoe 48, a portion of which engages the spring leaf 40.

Upon inward and outward movement of the plunger 45, snap movement of the free and movable extremity 33 of the spring leaf 30 and of the contact 34 associated therewith between the fixed contacts 17 and 23 results.

Without the incorporation of the spring leaf 40 and with an air gap of 0.006" between the movable contact 34 when in contact with the normally closed contact 17 and the normally open contact 23, the differential m vement required by the plunger 45 between the actuated condition and the de-actuated condition of the switch is approximately 0.002". However, with the arrangement as shown in the drawing, with the same air gap, the differential between the actuated and de-actuated condition of the switch is approximately 0.0012. It can be seen that a reduction of approximately 40% in the diiferential movement is possible by utilizing the expedient disclosed herein. Even more dramatic reductions in difierential movement are obtained when the invention disclosed herein is utilized with a switch of the type disclosed in the R. M. Readeker Patent 2,701,475. Thus, whereas the air gap in such a switch might be 0.010 and the normal differential 0.0003", a differential of 0.00005 can be obtained by utilizing the teaching disclosed herein. In such an arrangement the differential can be reduced by a factor of 6.

While it has not been determined how far the spring leaf 40 should extend towards extremity 33 of spring leaf 30, it has been determined that it should be long enough to extend into the actuating area of the switch. The further it extends beyond the actuating area the more dramatic the results. Of course, a point is reached wherein a reversal is noted and ultimately an area is attained where dead break is encountered.

While the spring leaf 40 has been shown to be flat, camber can be given the spring leaf 40 at its free end either in an upward or downward direction with the same results being obtained, insofar as reduction of differential is concerned.

While a single embodiment has been disclosed, it should be apparent that other embodiments are possible and therefore the scope of the invention should be determined from the following claims.

I claim:

1. A snap switch arrangement comprising: a housing including an inherently monostable base and a cover; a snap acting system including a pair of spring leaf tension members with a compression member disposed therebetween, first extremities of said tension and compression members supported in cantilever fashion from said base and the second extremities of said tension and compression members interconnected and arranged to be moved with a snap action between a first stop portion and a second stop portion provided on said base; a single relatively flat spring leaf member supported in cantilever fashion on said base and at the same location as said tension members, said spring leaf member overlying and engaging a portion of said tension members and extending into the actuating area of said snap acting system; and an actuating member for said snap acting system positioned in said cover and arranged to engage said spring leaf member so as to cause actuation and to allow de-actuation of said snap acting system upon movement of said actuating member in opposite directions; said spring leaf member combining with said snap acting system to reduce the differential movement required between the actuating and de-actuating points of said snap acting system.

2. A snap switch arrangement comprising: a support member; an inherently monostable snap acting system 1ncluding a spring leaf tension member and a compress on member, first extremitie of said tension and compression members supported in cantilever fashion from said support member and the second extremities of said tension and compression members interconnected and arranged to be moved with a snap action between a first stop portion and a second stop portion provided on said support member; a single relatively flat spring leaf member supported in cantilever fashion on said support member and at the same location as said tension member, said sprlng leaf member overlying and engaging a portion of said tension member and extending into the actuating area of said snap acting system; and operating means for said snap acting acting system arranged to engage said spring leaf member so as to cause actuation and to allow deactuation of said snap acting system upon movement of said operating means in opposite directions; said spring leaf member combining with said snap acting system to reduce the diiferential movement required between the actuating and de-actuating points of said snap acting systern.

3. A snap switch arrangement comprising: a support member; an inherently monstable snap acting system including a spring leaf tension member and a compression member, first extremities of said tension and compression members supported in cantilever fashion from said support member and the second extremities of said tension and compression members interconnected and arranged to be moved with a snap action between a first stop portion and a second stop portion provided on said support member; a single relatively flat spring leaf member contiguous with a portion of said tension member; and operating means for said snap acting system arranged to cause actuation 0nd to allow tie-actuation of said snap acting system upon movement of said operating means in opposite directions; said spring leaf member being positioned between the support area of said tension member and the actuating area of said snap acting system; said spring leaf member combining with said snap acting system to reduce the differential movement required between the actuating and de-actuating points of said snap acting system,

4. A snap switch arrangement comprising: a support member; an inherently monostable snap acting system including a spring leaf tension member and a compression member, first extremities of said tension and compression members supported in cantilever fashion from said support member and the second extremities of said tension and compression members interconnected and arranged to be moved with a snap action between a first stop portion and a second stop portion; a single relatively fiat resilient member contiguous with a portion of said tension member; and operating means for said snap acting system arranged to act upon said resilient member to cause actuation and to allow dc-actuation of said snap acting system upon movement of said operating means in opposite directions; said resilient member being positioned between the support area of said tension member and the actuating area of said snap acting system; said resilient member combining with said snap acting system to reduce the differential movement required between the actuating and de-actuating points of said snap acting system.

5. A snap switch arrangement comprising: a support member; an inherently monostable snap acting system including a tension member and a compression member, one of said members being resilient, first extremities of said tension and compression members supported in cantilever fashion from said support member and the second extremities of said tension and compression members interconnected and arranged to be moved with a snap action between a first stop portion and a second stop portion; a single relatively fiat resilient member contiguous with a portion of one of said tension and compression members;

5 6 and operating means for said snap acting system arranged actuating :and de-actuating points of said snap acting to act upon said relatively flat resilient member to cause system. actuation and to allow de-actuation of said snap acting References Cited in the file of this patent system upon movement of said operating means in oppo- UNITED STATES PATENTS site directions; said relatively flat resilient member being 5 positioned between the support area of the one of said 1960'020 McGaH May 1934 tension and compression members and the actuating area 12 F 261 1949 of said snap acting system; said relatively flat resilient 2627754 Mlnard 1953 member combining with said snap acting system to re- 2701475 Readeker 1955 duce the differential movement required between the 10 FOREIGN PATENTS 655,549 Great Britain July 25, 1951 

